The present invention relates to an arrangement and a method for controlling a radiation device.
Such an arrangement is used in particular in a radiotherapy system for the treatment of tumours. Rays that come into consideration for use are particle rays, such as, for example, protons or heavy ions. In tumour therapy, particle rays offer special physical advantages over electromagnetic rays; for example, they have a so-called xe2x80x9cinvertedxe2x80x9d dose profile, that is, the radiation dose deposited in the target volumexe2x80x94the tumour tissuexe2x80x94increases as the depth of penetration increases and has a sharp peak just before its maximum reach. With electromagnetic rays, on the other hand, the deposited radiation dose decreases as the depth of penetration increases, and a large part of the radiation dose is deposited in healthy tissue in front of and behind the tumour. In addition, particle rays are subject to substantially less deflection as they pass through thick tissue layers, and can be focussed extremely accurately on the tumour using magnetic lenses. Particle rays can therefore in principle be focussed on a target volume more effectively than electromagnetic rays. Moreover, heavy ions, for example, carbon or oxygen ions, additionally have significant biological benefits over protons in the destruction of tumour cells that are especially resistant to radiation.
For exact distribution of the heavy ion radiation dose over the target volume, it is known to proceed in accordance with the so-called raster scan method, used similarly in body-section radiography. A description of this method will be found in an article by Th. Haberer, W. Becher, D. Schardt and D. Kraft entitled xe2x80x9cMagnetic scanning system for heavy ion therapyxe2x80x9d, which appeared in xe2x80x9cNuclear Instruments and Methods in Physics Researchxe2x80x9d A330 (1993), p. 296-305. Here, the target volume is xe2x80x9cseparatedxe2x80x9d into individual slices of identical particle reach. In each slice, a grid pattern of points is defined, for each of which a number of particles to be deposited by the irradiation (radiation dose) is determined. The totality of the points and the particle numbers and particle energies allocated to them, that is, the distribution of the particle numbers over the total target volume, form a radiation plan. Starting with the rearmost slice, the particle ray, deflected by a pair of magnetic deflecting devices, scans each slice raster-fashion. The dose is varied from point to point in each slice, by directing the particle ray onto a point until the desired particle number value in accordance with the irradiation plan is reached.
It is difficult, however, to achieve an exact, reliable and sufficiently rapid control of the radiation device. Note that in the following text the term xe2x80x9ccontrol of a devicexe2x80x9d is used for the control and/or the monitoring of the same.
Up till now it has also been a problem to synchronise the control devices for beam deflection and particle number with one another such that during the course of irradiation they each relate at the same time to the same point in accordance with the irradiation plan. Otherwise, there is a risk that the patient will be harmed by an uncontrolled radiation process.
It is therefore the aim of the invention to produce an arrangement and a method for controlling a radiation device, which ensure an exact, rapid and reliable control of the beam.
According to the invention, the arrangement for controlling a radiation device comprises a chain of circuit modules, each circuit module having a separate communication connection to a preceding circuit module and a separate communication connection to a following circuit module.
In the method according to the invention for controlling a radiation device by means of control modules arranged in a chain, each control module communicates separately with a preceding control module and separately with a following control module.
The arrangement according to the invention and the method according to the invention are associated with a series of advantages. The provision of a separate communication connection to a preceding circuit module and a separate communication connection to a following circuit module allows reliable exchange of data between two circuit modules each time. Moreover, the communication of the other circuit module pairs is independent thereof, resulting in a separation of the data path and hence greater reliability of the arrangement.
According to a preferred exemplary embodiment of the invention, the radiation device can be in the form of a heavy ion radiation device. Using this device, it is possible advantageously to carry out especially precise and effective tumour treatments.
According to a further aspect of the invention, in the arrangement at least one of the circuit modules can have a connection to an external memory facility. It is thus possible for data to be read out and monitored without influencing the operational sequence of the beam control.
According to a further aspect of the invention, in the arrangement all circuit modules can have a common trigger bus. Exact synchronisation of all circuit modules can therefore advantageously be achieved.